Re: [PATCH v9] MIPS: force use FR=0 for FPXX binaries

[Thomas Bogendoerfer <tsbogend@alpha.franken.de>]

On Mon, Mar 29, 2021 at 01:09:18PM +0800, YunQiang Su wrote:
> YunQiang Su <yunqiang.su@cipunited.com> 于2021年3月22日周一 上午10:00写道：
> >
> > The MIPS FPU may have 3 mode:
> >   FR=0: MIPS I style, all of the FPR are single.
> >   FR=1: all 32 FPR can be double.
> >   FRE: redirecting the rw of odd-FPR to the upper 32bit of even-double FPR.
> >
> > The binary may have 3 mode:
> >   FP32: can only work with FR=0 and FRE mode
> >   FPXX: can work with all of FR=0/FR=1/FRE mode.
> >   FP64: can only work with FR=1 mode
> >
> > Some binary, for example the output of golang, may be mark as FPXX,
> > while in fact they are FP32. It is caused by the bug of design and linker:
> >   Object produced by pure Go has no FP annotation while in fact they are FP32;
> >   if we link them with the C module which marked as FPXX,
> >   the result will be marked as FPXX. If these fake-FPXX binaries is executed
> >   in FR=1 mode, some problem will happen.
> >
> > In Golang, now we add the FP32 annotation, so the future golang programs
> > won't have this problem. While for the existing binaries, we need a
> > kernel workaround.
> >
> 
> We meet a new problem in Debian: with the O32_FP64 enabled kernel,
> mips64el may also be affected.
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=983583

hmm, raising this issue in this context before knowing more details,
feels very trigger happy to me and this doesn't help accepting anything,
jfyi...

Could you please provide a link for downloading a golang binary, which
would need this patch to run ?

Thomas.

-- 
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good idea.                                                [ RFC1925, 2.3 ]